Csaba Ringhofer created IMPALA-6266:
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Summary: Runtime filters should not have non-deterministic
expression on consumer side
Key: IMPALA-6266
URL: https://issues.apache.org/jira/browse/IMPALA-6266
Project: IMPALA
Issue Type: Bug
Components: Frontend
Affects Versions: Impala 2.10.0
Reporter: Csaba Ringhofer
Random expressions on the consumer side of runtime filters are evaluated
independently from the "final" join, which gives +1 chance for rows to be
dropped. This means that the same query can return less or different rows if
the runtime fiiter was used than if not.
Example:
use tpch_parquet;
set DISABLE_ROW_RUNTIME_FILTERING=0;
select count(*) from supplier join nation on s_nationkey + cast(rand()*2 as
int) = n_nationkey;
result: 9722
set DISABLE_ROW_RUNTIME_FILTERING=1;
select count(*) from supplier join nation on s_nationkey + cast(rand()*2 as
int) = n_nationkey;
result: 9803
( rand() is pseudo-random, so running the same query without changing to query
option always returns the same result)
Optimizations like runtime filters should have no effect on the results, even
in case of non-deterministic expressions.
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